// Depends on rsa.js and jsbn2.js

// Version 1.1: support utf-8 decoding in pkcs1unpad2

// Undo PKCS#1 (type 2, random) padding and, if valid, return the plaintext
function pkcs1unpad2(d,n) {
    var b = d.toByteArray();
    var i = 0;
    while(i < b.length && b[i] == 0) ++i;
    if(b.length-i != n-1 || b[i] != 2)
        return null;
    ++i;
    while(b[i] != 0)
        if(++i >= b.length) return null;
    var ret = "";
    while(++i < b.length) {
        var c = b[i] & 255;
        if(c < 128) { // utf-8 decode
            ret += String.fromCharCode(c);
        }
        else if((c > 191) && (c < 224)) {
            ret += String.fromCharCode(((c & 31) << 6) | (b[i+1] & 63));
            ++i;
        }
        else {
            ret += String.fromCharCode(((c & 15) << 12) | ((b[i+1] & 63) << 6) | (b[i+2] & 63));
            i += 2;
        }
    }
    return ret;
}

// Set the private key fields N, e, and d from hex strings
function RSASetPrivate(N,E,D) {
    if(N != null && E != null && N.length > 0 && E.length > 0) {
        this.n = parseBigInt(N,16);
        this.e = parseInt(E,16);
        this.d = parseBigInt(D,16);
    }
    else
        alert("Invalid RSA private key");
}

// Set the private key fields N, e, d and CRT params from hex strings
function RSASetPrivateEx(N,E,D,P,Q,DP,DQ,C) {
    if(N != null && E != null && N.length > 0 && E.length > 0) {
        this.n = parseBigInt(N,16);
        this.e = parseInt(E,16);
        this.d = parseBigInt(D,16);
        this.p = parseBigInt(P,16);
        this.q = parseBigInt(Q,16);
        this.dmp1 = parseBigInt(DP,16);
        this.dmq1 = parseBigInt(DQ,16);
        this.coeff = parseBigInt(C,16);
    }
    else
        alert("Invalid RSA private key");
}

// Generate a new random private key B bits long, using public expt E
function RSAGenerate(B,E) {
    var rng = new SecureRandom();
    var qs = B>>1;
    this.e = parseInt(E,16);
    var ee = new BigInteger(E,16);
    for(;;) {
        for(;;) {
            this.p = new BigInteger(B-qs,1,rng);
            if(this.p.subtract(BigInteger.ONE).gcd(ee).compareTo(BigInteger.ONE) == 0 && this.p.isProbablePrime(10)) break;
        }
        for(;;) {
            this.q = new BigInteger(qs,1,rng);
            if(this.q.subtract(BigInteger.ONE).gcd(ee).compareTo(BigInteger.ONE) == 0 && this.q.isProbablePrime(10)) break;
        }
        if(this.p.compareTo(this.q) <= 0) {
            var t = this.p;
            this.p = this.q;
            this.q = t;
        }
        var p1 = this.p.subtract(BigInteger.ONE);
        var q1 = this.q.subtract(BigInteger.ONE);
        var phi = p1.multiply(q1);
        if(phi.gcd(ee).compareTo(BigInteger.ONE) == 0) {
            this.n = this.p.multiply(this.q);
            this.d = ee.modInverse(phi);
            this.dmp1 = this.d.mod(p1);
            this.dmq1 = this.d.mod(q1);
            this.coeff = this.q.modInverse(this.p);
            break;
        }
    }
}

// Perform raw private operation on "x": return x^d (mod n)
function RSADoPrivate(x) {
    if(this.p == null || this.q == null)
        return x.modPow(this.d, this.n);

    // TODO: re-calculate any missing CRT params
    var xp = x.mod(this.p).modPow(this.dmp1, this.p);
    var xq = x.mod(this.q).modPow(this.dmq1, this.q);

    while(xp.compareTo(xq) < 0)
        xp = xp.add(this.p);
    return xp.subtract(xq).multiply(this.coeff).mod(this.p).multiply(this.q).add(xq);
}

// Return the PKCS#1 RSA decryption of "ctext".
// "ctext" is an even-length hex string and the output is a plain string.
function RSADecrypt(ctext) {
    var c = parseBigInt(ctext, 16);
    var m = this.doPrivate(c);
    if(m == null) return null;
    return pkcs1unpad2(m, (this.n.bitLength()+7)>>3);
}

// Return the PKCS#1 RSA decryption of "ctext".
// "ctext" is a Base64-encoded string and the output is a plain string.
//function RSAB64Decrypt(ctext) {
//  var h = b64tohex(ctext);
//  if(h) return this.decrypt(h); else return null;
//}

// protected
RSAKey.prototype.doPrivate = RSADoPrivate;

// public
RSAKey.prototype.setPrivate = RSASetPrivate;
RSAKey.prototype.setPrivateEx = RSASetPrivateEx;
RSAKey.prototype.generate = RSAGenerate;
RSAKey.prototype.decrypt = RSADecrypt;
//RSAKey.prototype.b64_decrypt = RSAB64Decrypt;